Free radical scavenging activities of differently deacetylated chitosans using an ESR spectrometer

Proteomic analysis of the peritrophic matrix from the gut of the caterpillar, Helicoverpa armigera

The peritrophic matrix from the midgut of the caterpillar, Helicovera armigera, was solubilized by treatment with anhydrous trifluoromethanesulfonic acid, apparently by depolymerisation of its chitin component. This allowed the efficient extraction of proteins in a technique that may be broadly applicable to the analysis of other structures containing chitin. Gel electrophoresis and mass spectrometry of tryptic peptides were used to identify the extracted proteins with gut-expressed cDNA sequences. The major proteins of this cohesive, digestion-resistant structure are chitin deacetylase-like and mucin-like proteins, the latter with multiple chitin-binding domains that may cross-link chitin fibrils to provide a barrier against abrasive food particles and parasites, one of the major functions of the matrix. Other proteins found in the H. armigera gut peritrophic matrix suggest that the matrix is a dynamic, complex structure that may participate in the immobilization of digestive enzymes, actively protect the gut from parasite invasion and intercept toxins such as lectins and Bacillus thuringiensis crystal proteins.

Chitosan treatments affect growth and selected quality of sunflower sprouts

The effects of chitosan molecular weights, solvent types, and concentrations of chitosan solution, and seed soaking times on growth and selected quality of sunflower sprouts were investigated. Among 5 chitosans tested (746, 444, 223, 67, and 28 kDa), 28 kDa chitosan exhibited the highest DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity both at 0.1% and 1.0% concentrations. Optimal conditions selected for cultivation of sunflower sprouts involved soaking seeds in 0.5% chitosan with 28 kDa (dissolved in 0.5% lactic acid) for 18 h. After cultivation for 6 d at 20 degrees C, sunflower seeds soaked in chitosan solution for 18 h under the optimal conditions yielded sprouts with 12.9% higher total weight and 16.0% higher germination rate, compared with those of seeds soaked in water for 18 h (control). Furthermore, the total amino acid content of the former sprouts (12098 mg/100 g) was slightly higher than that of the latter (12057 mg/100 g). Sprouting of sunflower seeds improved DPPH radical scavenging activity, probably due to the increased total phenolic, melatonin, and total isoflavone contents. Similarly, chitosan-treated sprouts exhibited slightly improved DPPH radical scavenging activity, probably due to slightly increased total phenolic and melatonin contents, and moderately increased total isoflavone content compared with those of the control. Chitosan treatment increased the total isoflavone content of sprouts by 11.8%, due mainly to the increased daidzein content, compared with that of the control.

Sulfated chitooligosaccharides as prolyl endopeptidase inhibitor

Prolyl endopeptidase (PEP, EC 3.4.21.26) is a proline-specific endopeptidase with a serine-type mechanism, which digests small peptide-like hormones, neuroactive peptides, and various cellular factors. PEP has been involved in neurodegenerative disorders, therefore, the discovery of PEP inhibitors can revert memory loss caused by amnesic compounds. In this study, we prepared hetero-chitooligosaccharides (COSs) with different molecular sizes using ultrafiltration (UF) membrane reactor system from hetero-chitosan with different degrees of deacetylation (DD; 90%, 75% and 50% deacetylation), and synthesized sulfated COSs (SCOSs). PEP inhibitory activities of SCOSs were evaluated and the results showed that 50% deacetylated SCOSs (50-SCOSs) exhibited higher inhibitory activities than those of 90% and 75% deacetylated SCOSs (90-SCOSs and 75-SCOSs). Among the 50-SCOSs (50-SCOS I, 5000-10,000Da; 50-SCOS II, 1000-5000Da; 50-SCOS III, below 1000Da), 50-SCOS II possessed the highest inhibitory activity and IC(50) value was 0.38mg/ml. Kinetics studies with 50-SCOS II indicated a competitive enzyme inhibition with a K(i) value of 0.78mg/ml. It was concluded that the 50-SCOS II may be useful for PEP inhibitor and for developing a new type PEP inhibitor from carbohydrate based materials.

Differential effects of chitooligosaccharides on serum cytokine levels in aged subjects

Free amine chitooligosaccharides (FACOS, Kitto Life, Seoul, Republic of Korea) with an average molecular mass of 3.5 kDa were efficiently produced using an ultrafiltration membrane reactor system. To evaluate the effect of chitooligosaccharides on serum cytokine levels in elderly adults after oral intake, 5.1 g/day of FACOS was given to elderly (age range, 74-86 years; mean, 80 +/- 3 years) volunteers during an 8-week experimental period. Interleukin (IL)-12 and interferonã levels were significantly higher in the FACOS group than in the control group (P < .05). However, levels of the inflammatory cytokines IL-1beta and tumor necrosis factor-alpha decreased after FACOS intake during the experimental period. The results of this study suggest that the oral intake of chitooligosaccharides may have beneficial effects on specific cell-mediated immunity while also acting as an anti-inflammatory agent in aged subjects.

Analysis of antioxidant properties of chitosan and its oligomers

Oral treatment with chitosan with a molecular weight approximately 105, but not its oligomer, reduced plasma content of free-radical oxidation products in normal rats and animals treated for the bone marrow form of radiation sickness and stimulated the recovery processes in involved bone marrow and peripheral blood.

Reactive oxygen species scavenging activity of aminoderivatized chitosan with different degree of deacetylation

Chitosans with different degree of deacetylation were prepared from crab shell chitin in the presence of alkali. Aminoderivatized chitosan derivatives were prepared in addition of amino functional groups at a hydroxyl site in the chitosan backbone. Six kinds of aminoderivatized chitosan such as aminoethyl-chitosan (AEC90), dimethylaminoethyl-chitosan (DMAEC90), and diethylaminoethyl-chitosan (DEAEC90), which were prepared from 90% deacetylated chitosan, and AEC50, DMAEC50 and DEAEC50, which were prepared from 50% deacetylated chitosan, were prepared and their reactive oxygen species (ROS) scavenging activities were investigated against hydroxyl radical, superoxide anion radical and hydrogen peroxide. The electron spin resonance (ESR) spectrum revealed that AEC90 showed the highest scavenging effects against hydroxyl and superoxide anion radical, the effects were 91.67% and 65.34% at 0.25 and 5 mg/mL, respectively. For hydrogen peroxide scavenging effect, DEAEC90 exhibited the strongest activity. These results suggest that the scavenging effect depends on their degree of deacetylation and substituted group.

Cytotoxic activities of water-soluble chitosan derivatives with different degree of deacetylation

Chitosans with different degree of deacetylation (DD) (90% and 50% deacetylated chitosan) were prepared by N-deacetylation followed by grafted onto chitosan to form water-soluble aminoethyl-chitosan (AE-chitosan), and dimetylaminoethyl-chitosan (DMAE-chitosan), diethylaminoethyl-chitosan (DEAE-chitosan). In the present study, cytotoxic activities of the chitosan derivatives were evaluated using three tumor cell lines and two normal cell lines, and structure-activity relationship was suggested. The cytotoxic activity was dependent on their DD and substituted group.

Antioxidant activity of novel chitin derivative

Novel water-soluble chitin derivative was prepared by chemical modification to evaluate antioxidant activities by free radical scavenging potential using electron spin resonance spin trapping technique. Aminoethyl-chitin (AEC) exhibited free radical scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, superoxide, and peroxyl radicals. AEC quenched DPPH and peroxyl radical over 55% and 59% at 4mg/mL, and also suppressed superoixde radical over 58% at 2mg/mL. Especially, AEC was more active against hydroxyl radical, and scavenging ratio was 92.2% at 0.12mg/mL. These results suggested that free amino group in the -CH(2)CH(2)NH(2) plays an important role in the free radical scavenging activity. In addition, cytotoxic effect of AEC was assessed using human lung fibroblast (MRC-5) cell line, and AEC showed less toxic against MRC-5.

Antihypertensive activity of chitin derivatives

To develop angiotensin I converting enzyme (ACE) inhibitory chitin derivatives based on the properties of ACE inhibitors, chitins with different degree of deacetylation were chemically modified by grafting 2-chloroethylamino hydrochloride onto chitin at the C-6 position. Three kinds of chitin derivatives were prepared and designated as aminoethyl-chitin (AEC) with 10% degree of deacetylation, aminoethyl-chitin with 50% degree of deacetylation (AEC50), and aminoethyl-chitin with 90% degree of deacetylation (AEC90). IC50 values of three chitin derivatives on ACE were 0.064 microM (AEC), 0.038 microM (AEC50), and 0.103 microM (AEC90). The results of Dixon plots revealed that AEC50 was a competitive inhibitor, and the inhibition constant (Ki) value was 0.021 microM. In addition, the antihypertensive effect of AEC50 on spontaneously hypertensive rats (SHR) was evaluated, and the result showed that it effectively decreased systolic blood pressure (SBP) in a dose-dependent manner.

Water-soluble chitosan derivatives as a BACE1 inhibitor

BACE1 (the beta-site APP-cleaving enzyme) inhibitory activities of water-soluble chitosan derivatives substituted with aminoethyl, dimethylaminoethyl and diethylaminoethyl groups were investigated. AE-chitosan (90%) prepared from 90% deacetylated chitosan showed the strongest BACE1 inhibitory activity than those of other derivatives. The inhibitory pattern was found to be non-competitive by Dixon plot, and the value of the inhibition constant (K(i)) was 85 microg/mL.

Effect of chitooligosaccharides on calcium bioavailability and bone strength in ovariectomized rats

Chitosan polymer with deacetylation degree of 93% was hydrolyzed with an endo-type chitosanase (35,000 U/g protein) with substrate to enzyme ratio of 1 to 1.5 for 18 h in a batch reactor, and then the resultant hydrolysates were fractionated into four different molecular weights using an ultrafiltration (UF) membrane reactor system. An in vitro study elucidated that four kinds of chitooligosaccharides (COSs) could efficiently inhibit the formation of insoluble calcium salts in the neutral pH. In vivo effects of COSs on Ca bioavailability were further studied in the osteoporosis modeling rats induced by ovariectomy and concurrent low calcium intake. During the experimental period corresponding to the menopause with the osteoporosis disease, calcium retention was increased and bone turnover was decreased by COS IV supplementation in the ovariectomized (OVX) rats. After the low Ca diet, COS IV diet including both normal level of calcium and vitamin D significantly decreased calcium loss in feces and increased calcium retention compared to the control diet. The levels of femoral total calcium, bone mineral density (BMD), and femoral strength were also significantly increased by the COS IV diet in a similar level to those of CPP diet group. In the present study, the results proved the beneficial effects of low molecular chitooligosaccharide (COS IV) in preventing negative mineral balance.

Factors affecting the free radical scavenging behavior of chitosan sulfate

Scavenging activity of hydroxyethyl chitosan sulfate (HCS) against 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl and carbon-centered radical species were studied using electron spin resonance (ESR) spectroscopy. In addition, its antioxidant activity to retard lipid peroxidation was also evaluated in a linoleic acid model system. HCS could scavenge DPPH (33.78%, 2.5 mg/mL) and carbon-centered radicals (67.74%, 0.25 mg/mL) effectively. However, chitosan sulfate did not exhibit any scavenging activity against hydroxyl radicals, but increased its generation. This was different from the published literature and was presumed due to the loss of chelating ability on Fe2+. This assumption could further confirm from the results obtained for Fe2+-ferrozine method that upon sulfation chitooligosaccharides lost its chelation properties. Therefore, HCS can be identified as antioxidant that effectively scavenges carbon centered radicals to retard lipid peroxidation.

Free radical scavenging properties of hetero-chitooligosaccharides using an ESR spectroscopy

Nine kinds of hetero-chitooligosaccharides (hetero-COSs) with relatively higher molecular weights (90, 75 and 50-HMWCOS), medium molecular weights (90, 75 and 50-MMWCOS), and lower molecular weights (90, 75 and 50-LMWCOS) were prepared from partially deacetylated hetero-chitosans (90, 75 and 50% deacetylated chitosan), and their scavenging activities were investigated against 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, superoxide and carbon-centered radicals using electron spin resonance (ESR) spin-trapping technique. Superoxide, hydroxyl and carbon-centered radicals were generated from hypoxanthine-xanthine oxidase reaction, hydrogen peroxide-ferrous sulfate (Fenton reaction) and azo compound 2,2-azobis-(2-amidinopropane)-hydrochloride (AAPH), respectively. The ESR results revealed that 90-MMWCOS, which is having relatively medium molecular weights prepared from 90% deacetylated chitosan, showed the highest scavenging activity on all tested radicals. In addition, the radical scavenging activity of hetero-COSs increased with a dose-dependent manner, and it was dependent on their degree of deacetylation values and molecular weights.